Pyrolysis, or controlled heating of feedstock in the absence of oxygen, resulting in thermal decomposition of the feedstock fuel into volatile gases and solid carbon material by-product, was first practiced on a commercial scale in 1812, when a city gas company in London started the production of town gas applications.
The first commercial gasifier (updraft type) for continuous gasification of solid fuels, representing an air-blown process, was installed in 1839 producing what is known as “producer gas” combustion type gasifiers. They were further developed for different input fuel feedstocks and were in widespread use in specific industrial power and heat applications throughout the late 1800's and into the mid-1920's, when petroleum fueled systems gradually took over the producer gas fuel markets.
Between 1920 and 1940, small and compact gasifier systems for automotive applications were developed in Europe. During the Second World War, perhaps tens of thousands of these combustion type gasifiers were used in Europe and across other scattered market applications. Shortly after the War most gasifiers were decommissioned because of widespread availability of commercial gasoline and diesel fuels.
Gasification emphasis again came to the forefront due to the energy crisis of the 1970's. Gasifier technology was perceived as a relatively cheap alternative for small-scale industrial and utility power generation, especially when sufficient sustainable biomass resources were available. By the beginning of the 1980's nearly a dozen (mainly European) manufacturers were offering small-scale wood and charcoal fired “steam generation” power plants.
In Western countries, coal gasification systems began to experience expanded interest during the 1980's as an alternative for the utilization of natural gas and oil as the base energy resource. Technology development perhaps mainly evolved as fluidized bed gasification systems for coal, but also for the gasification of biomass. Over the last 15 years, there may have been much development of gasification systems as directed toward the production of electricity and generation of heat in advanced gas turbine based co-generation units.
Gasification of biomass perhaps can appear deceptively simple in principle and many types of gasifiers have been developed. The production of combustible syn-gas from biomass input fuel may have attractive potential benefits perhaps such as ridding the environment of noxious waste disposal problems, possible ease of handling, and perhaps providing alternative energy production with possibly the release of low levels of atmospheric environmental contaminants. Further, cheap electricity generation and the application of the produced syn-gas as an economical energy source for the manufacture of liquid fuels may also often make gasification very appealing.
However, the biomass input feedstock which is used in gasifiers may challenge perceptions of uncomplicated design simplicity since the feedstock material may represent varying chemical characteristic and physical properties, perhaps as inherent and unique to each individual biomass feedstock material. The chemical reactions involved in gasification, relative to processing the different varieties of available biomass materials, may involve many different reactants and many possible reaction pathways. The reaction rates are often relatively high; all these variable factors may contribute to the perhaps very complex and complicating nature of gasification processes. All too often uncontrollable variables may exist that may make gasifiers hard to mass balance control and perhaps to operate satisfactorily within known preventive maintenance procedures, steady-state output constants, and manageable environmental control compliance areas.
Numerous U.S. patents have been issued relating to alternative or renewable energy technology descriptions involving gasification or syn-gas technologies. The present inventive technology perhaps may overcome many of the operational disadvantages associated with and perhaps commonplace to current and commercially viable processes involving existing gasification systems. The various types of available market updraft, downdraft, air-blown, fixed bed, fluidized bed, circulating fluidized bed, pulsed-bed, encapsulated entrained flow, and other gasification systems may often have one or more serious disadvantages that perhaps may be overcome by the present inventive technology.
In conventional gasification systems, disadvantages often may exist that may create problems in perhaps a variety of areas, including but not limited to areas such as: process control stability related to input feedstock changes, steady state loading, blockage and overall system throughput limitations; slagging potential and challenges; scale-up sizing challenges; moisture limitations; system gas and internal vapor leak challenges; carry-through impurities and contamination challenges, system plugging challenges (such as with excess char, tars or phenols); problems with generated hydrocarbon volatiles and other corrosive sulfur vapor carry-through contaminants being released into produced synthesis gas; decreased BTU energy values in final produced synthesis gas (such as due to excess CO2, N2, or particulate contamination); and the like.
For example, conventional gasification systems may use horizontal-plane screw for moving feedstock material, at controlled throughput feed rates, into other competitive gasification thermal reactor systems and also for simultaneously utilizing the enclosed auger pipe housing (often using more than one auger system in a one-to-the-other configuration) as an enclosed temperature stage initial devolatilization zone. However, these combined double-duty auger system designs may often be plagued with numerous and sporadic mechanical, unpredictable and uncontrollable process (negative) variables. Such variables can be considered as centering around problems associated with input feed solids that can often rope/lock disproportionally together or that can otherwise cause plugging or binding of the auger shaft, helical flights and/or blind the auger close tolerance receiver pipe cylinder openings. This can in-turn warp the auger drive shaft into a bent and/or an elliptical configuration. Auger shaft warpage can cause a high side rotational internal friction wear and can rapidly create stress cracks in an auger-pipe cylinder housing unit. This can cause constant process pressure variation and can cause vapor leaks. Excess friction drag can also break shafts. Further, intermittent carbonaceous material bulk jams can occur whereby the throughput devolatilization reactivity can be either lost or slowed. Feedstock decomposition and devolatilization reactions can also begin to occur at the surface of the plug/jam, therefore releasing, and perhaps slowly devolatilizing, char solids, phenols, tars, surfactants and other surface chemical hydrocarbon constituents that can further liquefy and wax or seal the outer bulk-mass surface of the plug materials into an even tighter and more cementaceous plug. Incoming feedstock “plug mass” can quickly fill into and blind the relatively small cross-section diameter surface area narrower openings within typical auger screw pipe cylinder housings. This can also begin to close off the auger screw conduit that also serves as an initial devolatilization chamber.
The foregoing problems regarding conventional technologies may represent a long-felt need for an effective solution to the same. While implementing elements may have been available, actual attempts to meet this need to the degree now accomplished may have been lacking to some degree. This may have been due to a failure of those having ordinary skill in the art to fully appreciate or understand the nature of the problems and challenges involved. As a result of this lack of understanding, attempts to meet these long-felt needs may have failed to effectively solve one or more of the problems or challenges here identified. These attempts may even have led away from the technical directions taken by the present inventive technology and may even result in the achievements of the present inventive technology being considered to some degree an unexpected result of the approach taken by some in the field.